Quarterly Results of Operations (Unaudited) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Quarterly Financial Information Disclosure [Abstract]
Net sales	$ 614,094	$ 622,888	$ 634,360	$ 612,324	$ 585,904	$ 574,490	$ 573,366	$ 553,552	$ 2,483,666	$ 2,287,312	$ 2,113,043
Gross profit	273,643	280,233	287,367	276,652	260,882	257,930	256,925	250,941	1,117,895	1,026,678	930,767
Operating income	139,441	145,133	147,831	136,683	135,248	126,504	125,133	115,671	569,088	502,556	412,397
Net income	$ 98,137	$ 106,352	$ 107,126	$ 98,958	$ 93,746	$ 83,768	$ 83,844	$ 75,899	$ 410,573	$ 337,257	$ 271,109
Basic EPS (in dollar per share)	$ 1.29	$ 1.39	$ 1.40	$ 1.29	$ 1.23	$ 1.09	$ 1.10	$ 0.99	$ 5.36	$ 4.41	$ 3.57
Diluted EPS (in dollar per share)	$ 1.27	$ 1.37	$ 1.38	$ 1.27	$ 1.21	$ 1.08	$ 1.08	$ 0.99	$ 5.29	$ 4.36	$ 3.53
Basic weighted average shares outstanding (in shares)	76,128	76,562	76,539	76,419	76,283	76,309	76,220	76,115	76,412	76,232	75,803
Diluted weighted average shares outstanding (in shares)	77,100	77,709	77,704	77,739	77,597	77,523	77,320	76,894	77,563	77,333	76,758